WASHINGTON—In any dictatorship that holds an election, opposition movements face a dilemma—to participate or not to participate. If they do, they could legitimize an electoral charade. If they don’t, they will cede all the institutional space to the dictator.

Five years ago, the Venezuelan opposition boycotted National Assembly elections. Their case was morally sound: Everything pointed to a rigged vote and any collaboration with Hugo Chavez’s farce would openly help him. But the result was a legislature that has overwhelmingly acted as Chavez’s mouthpiece. When those elections took place, Chavez was well beyond the point at which public opinion mattered.

Which is why Venezuela’s opposition Coalition for Democratic Unity has made the right decision by participating in the Sept. 26 elections to renew the National Assembly. Faced with the prospect of a totalitarian state, abstention is not an option. Winning the moral argument—the basic goal of abstaining—is futile when the theater of political war is no longer that of right and wrong but simply that of dying republican institutions versus a tyrannical juggernaut. In this scenario, the urgent need is the preservation of whatever political capital those fighting for the survival of the Venezuelan republic still have; the larger one is to reverse the trend in their favor. By partaking in the vote, the opposition is doing the former and at least keeping alive the chance of the latter.

We know that this will not be a fair election. Even though polls indicate that the opposition is slightly ahead of the government, and even though two-thirds of Venezuelans say that Chavez should leave power rather than seek another term next year, the prevailing conditions will not allow the government’s foes to capture a majority of the assembly. Pro-Chavez states have a disproportionate representation: The opposition would need a bit less than 60 percent of the vote to get a majority. Given the shady electoral body, the campaign of violence and intimidation against critics, and various restrictions imposed on the news media and other organizations, there is scant chance that the official tally will match the number of real votes commanded by the coalition.

But the campaign has confirmed that a majority of Venezuelans repudiate the regime even if, at 40 percent or so, the level of support for Chavez remains relatively strong. It has helped concentrate people’s minds on the tragic balance of Bolivarian socialism: uncontrollable crime (1,600 deaths in 2009); the ruin of services (daily power outages even though the Guri Dam, which supplies two-thirds of the country’s electricity, now backs up plenty of water); food shortages (and hoarding by officials who sell it on the black market); inflation (above 30 percent); and an economic contraction this year, when the rest of Latin America is headed for an average growth rate of more than 5 percent.

The elections will give opponents a presence in the National Assembly. Yes, Chavez will likely turn to his “communal assemblies,” local bodies designed to replace the republican institutions as an alternative source of legislative power. But the Assembly will still project the opposition’s voice beyond its current confines and raise the cost of the dictatorship’s routine harassment of elected officials who are not his lap dogs. If the opposition gets a third of the Assembly, Chavez will have to disqualify, throw in jail, beat up or expel a very significant number of elected parliamentarians belonging to a high-profile body based in Caracas—as opposed to a governor here or a few mayors there.

No one should be under the illusion that there is a proportional relationship between the number of people who want to see Chavez out of power and the chances that this will happen anytime soon. Ever since he came back to power after the short-lived coup of 2002 and, perhaps more decisively, his victory in the recall referendum of 2004, the relative strength of the forces at play changed in the strongman’s favor. What is still possible, with much help from the Parcae, or fates, is to gradually debilitate him to the point at which forces within the regime are ready to leave him powerless against a majority of Venezuelans ready to confront him.

Participating in this election is a baby step in that direction. It is well worth taking.